[Bug tree-optimization/109938] New: ((a^c) & b) | a is not opimized to (b & c) | a

[Bug tree-optimization/109938] New: ((a^c) & b) | a is not opimized to (b & c) | a

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109938

            Bug ID: 109938
           Summary: ((a^c) & b) | a is not opimized to (b & c) | a
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pinskia at gcc dot gnu.org
  Target Milestone: ---

Take:
```
int f(int a, int b, int c)
{
  return ((a^c) & b) | a;
}
int f1(int a, int b, int c)
{
  return ((a^c) | a) & (b|a);
}
int f2(int a, int b, int c)
{
  return (b & c) | a;
}
```

These 3 functions should produce the same code.
Currently only f1 and f2 produces the decent code.

I noticed this while looking into PR 107887 and it is related to PR 100864.

[Bug tree-optimization/109938] ((a^c) & b) | a is not opimized to (b & c) | a

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109938

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2023-05-23
     Ever confirmed|0                           |1
           Keywords|                            |missed-optimization
             Status|UNCONFIRMED                 |NEW

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
Confirmed.

[Bug tree-optimization/109938] ((a^c) & b) | a is not opimized to (b & c) | a

[drross at redhat dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109938

Drew Ross <drross at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |drross at redhat dot com

--- Comment #2 from Drew Ross <drross at redhat dot com> ---
Expanding the pattern as follows: ((a^c) & b) | a --> (a | (a^c)) & (a | b)
allows  other patterns to make the simplification. Namely (a | (a^c)) -> a | c,
then
(a | c) & (a | b) -> a | (b & c). 

This type of expansion also generalizes nicely to patterns like ((a^c) | b) | a
-> a | b | c which can be done through a similar series of simplifications
after expanding the initial.

This brings up the infrastructure question for 3+ operators if it is worth it
to try all (or maybe most?) pairwise simplifications (for instance even in the
case of (a ^ c) | b | d | e | f | g | h | a).

Thoughts?

[Bug tree-optimization/109938] ((a^c) & b) | a is not opimized to (b & c) | a

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109938

--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jakub Jelinek <jakub@gcc.gnu.org>:

https://gcc.gnu.org/g:9f9334921b7d2e7bdb7e03be1bf5a2caa8ed3ca9

commit r14-3144-g9f9334921b7d2e7bdb7e03be1bf5a2caa8ed3ca9
Author: Drew Ross <drross@redhat.com>
Date:   Fri Aug 11 10:17:56 2023 +0200

    match.pd: Implement missed optimization ((x ^ y) & z) | x -> (z & y) | x
[PR109938]

    Adds a simplification for ((x ^ y) & z) | x to be folded into
    (z & y) | x. Merges this simplification with ((x | y) & z) | x -> (z & y) |
x
    to prevent duplicate pattern.

    2023-08-11  Drew Ross  <drross@redhat.com>
                Jakub Jelinek  <jakub@redhat.com>

            PR tree-optimization/109938
            * match.pd (((x ^ y) & z) | x -> (z & y) | x): New simplification.

            * gcc.c-torture/execute/pr109938.c: New test.
            * gcc.dg/tree-ssa/pr109938.c: New test.

[Bug tree-optimization/109938] ((a^c) & b) | a is not opimized to (b & c) | a

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109938

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
   Target Milestone|---                         |14.0
             Status|NEW                         |RESOLVED

--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Fixed.